J. Nannoplankton Res. 37 (2–3), 2017, pp.189–214 © 2017 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA

189

Late Miocene to Late Pliocene taxonomy and stratigraphyof the genus Discoaster in the circum North Atlantic Basin:
Gulf of Mexico and ODP Leg 154
Emily Browning*
BP America, Inc., 200 Westlake Park Blvd, Houston, TX 77079 USA; *Emily.Browning@bp.com

Jim Bergen
Paleo @ the Hill Country, Brenham, TX 77833 USA; jbnanno@att.net

Stacie Blair
Blair Biostratigraphy, Cypress, TX 77429 USA; stacie.blair81@gmail.com

Todd Boesiger
ALS Global, Lincoln, NE 68506 USA; tboesig@gmail.com

Eric de Kaenel
DPR, Chemin sous la Roche 4b, 1185 Mont-sur-Rolle, Switzerland; edekaenel@bluewin.ch
Manuscript received 26th September, 2016; revised manuscript accepted 8th July, 2017

Abstract Discoasters have long been utilized in Neogene nannofossil biostratigraphy in the Gulf of Mexicoand make up an important group of marker taxa from the Pliocene to Middle Miocene. In this paper, we discusstaxonomy and biostratigraphy of seven Discoaster groups and one group of Minylitha for the Late Pliocene to Late
Miocene. Detailed taxonomic descriptions of species in these groups are provided with accompanying photographs
and morphologic diagrams. Discussions of described species, subspecies, emendations and descriptions of new
species provide an education of species concepts utilized by British Petroleum for biostratigraphic control in the
Gulf of Mexico. The stratigraphic occurrences of these species are calibrated to the astronomical chronometer fromODP Leg 154 in the western equatorial Atlantic and tied to the Neogene Astronomical Time Scale. Fortyeight biostratigraphic events are discussed for the Gulf of Mexico and ODP Leg 154 from 17.393 to 1.924Ma.
Eleven new Discoaster and one new Minylitha taxa are described: D. bolivariae, D. breviloeblichii, D. caulifloris,
D. pachyloeblichii, D. pansulus, D. pliostellulus, D. quadribollii, D. dennei, D. tribollii, D. trifolius, D. triuncinus
and M. cancellata. We introduce one new subspecies, D. prepentaradiatus plautus, and three taxa emendations:
Discoaster hamatus, Discoaster styzenii and Discoaster neohamatus.

Keywords Nannofossils, Pliocene, Miocene, taxonomy, Gulf of Mexico, biostratigraphy, Discoaster, Minylitha,
ODP Leg 154

1. Introduction
Calcareous nannofossil biostratigraphy has become anincreasingly important tool for subsurface description
in the petroleum industry over the last few decades withthe move to explore and develop deep-water basins. The
focus of this study is the application of biostratigraphy in
the Gulf of Mexico (GoM). The 1990s mergers of British
Petroleum (BP) with Amoco and Arco Vastar provided BP
the opportunity to integrate Cenozoic calcareous microfossil biostratigraphies for the Gulf of Mexico developed
independently within these three heritage companies. In
the early 2000s, to aid exploration efforts and development in stratigraphically- and- structurally complex fields
in the Gulf of Mexico, BP supported research to improvetheir biostratigraphic database. The results from this heritage integration and research were the development of

the in-house BP Gulf of Mexico Neogene Astronomically
Tuned Time Scale.
A fourteen-year in-house research program was initiated to ground this Cenozoic framework to an “astronomically-tuned” age model by utilizing core material from
Ocean Drilling Program (ODP) Leg 154, Ceará Rise. This
integrated framework is based on the historical analysis of
thousands of wells in the Gulf of Mexico, and is calibrated
from Leg 154 core material. This represents a cyclostratigraphic-based age model for the early Oligocene (30.679Ma)
through early Pleistocene (1.595Ma).The “BPGulf of Mexico
Neogene Astronomically Tuned Time Scale” (BP GNATTS;
Bergen et al., in prep) is currently in preparation for publication and contains the details of the BP Gulf of Mexico age
model, biostratigraphic horizon nomenclature, and event
stratigraphy and calibration (Bergen et al., in prep).

190

Browning et al.

The extensive taxonomic and stratigraphic discussionof BP concepts and revisions of Neogene species within
the five taxonomic papers presented in this volume aremeant to provide a manual for learning and clarifying concepts which must precede publication of the BP GNATTS.
These works, in sum, represent over five decades of compiled knowledge in the GoM from within the heritage
companies and BP. This paper focuses on species of Discoaster nannofossil taxa and events from the Late Pliocene (1.924Ma; NN18) to Middle Miocene (17.373Ma;
NN4). It includes biostratigraphic refinement, taxonomic
definitions, and new species descriptions primarily of
Discoasters, but also includes species of Minylitha. This
study expands upon the two group’s biostratigraphic
utility by providing 48 biostratigraphic events, 12 new
species descriptions, one new subspecies description
and three emendations. Discoaster quinqueramus, a keygroup for late Miocene biostratigraphy, has been separated and is discussed by Blair et al. (2017; this volume),
as well as taxa associated with the Miocene/Pliocene
boundary.
2. Materials and methods
The materials used for this study are from outcrops, core
and well cuttings. Most of these samples were collectedfrom ODP cores of Leg 154 at the IODP repository in Bremen (Germany), from the Lower Oligocene (30.679Ma)
to the Lower Pleistocene (1.595Ma).
ODP Leg 154 is situated on the Ceará Rise in the western tropical Atlantic Ocean. Other DSDP/ODP materials
used are from DSDP Leg 68, Hole 502 (Colombia Basin,
western Caribbean Sea) and the original Bolli Collection
from Trinidad (Figure 1). Details of the sampling programand sample preparation are provided in de Kaenel et al.
(2017; this volume).
The base of the Pleistocene was moved to the baseof the Gelasian Stage in 2009 by the Executive Committee of the International Union of Geological Sciences
120°0'0"W

30°0'0"N

90°0'0"W

60°0'0"W

Atlantic
Ocean

Gulf of Mexico

Leg 68 Site 502

TrinidadLeg 154 Site 926

0°0'0"

Figure 1: Locality map showing reference material for this study from
Ceará Rise (ODP Leg 154, Site 926), the Gulf of Mexico, western Caribbean Sea (DSDP Leg 68, Site 502) and Bolli Collection, Trinidad(IUGS); however, we have decided to keep the Pliocene/
Pleistocene boundary at the top of the Gelasian Stage at
1.806Ma, following the astronomically tuned age of Lourens et al. (1996). This transfer of the Gelasian Stage is notfollowed in this regional study because the BP GNATTS(Bergen et al., in prep) has not yet adopted the new Pliocene/Pleistocene boundary placement at the top of theGelasian Stage. This omission is necessary to avoid confusion and maintain consistency with the GoM industry
standard that continues to place the boundary at the top of
the Gelasian Stage on the last occurrence of Discoasterbrouweri.
Samples were analyzed by multiple nannofossil paleontologists. Events were cross-checked and verified, andtaxonomic concepts were synchronized, providing confidence in datum calibrations. All age calibrations are
new and based on 14 years of analyses of the ODP Leg
154 materials. The backbone of the BP and Arco methodologies was the abundance cycle, while Amoco wasstrongly event-driven, the sequence of fossil tops taking
precedence. The BP GNATTS (Bergen et al., in prep) isa hybrid of the methodologies and is based on a combination of tops, bases and abundance changes. The following stratigraphic abbreviations are used: LO (lowest
occurrence) and HO (highest occurrence); abundance
modifiers are R (regular) for LRO and HRO, F (few)for LFO and HFO, C (common) for LCO and HCO andAcme.
The objective of this work is to clarify taxonomic concepts and present the GoM stratigraphy developed overthe past five decades from BP and its heritage companies,
therefore this study does not compare our results to otherpublished stratigraphies of the GoM Basin or research on
ODP Leg 154 (e.g., Denne, 2008; Raffi et al., 2016). The
geologic ages derived from sampling of ODP Leg 154 aremaintained at three decimal precision through the manuscript for consistency; errors stated on ages reflect thedifference in age for the next sample analyzed upwards or
downwards in the composite section. Nannofossil stratigraphic range charts are available from the PANGAEA
web database (www.pangaea.de).
3. Biostratigraphy and taxonomy
In the Late Miocene, Discoasters provide key stratigraphic
events for dividing the long Zone NN10. In the GoM, species of Discoasters have long been used for division of theLate Pliocene, and a discussion of the general groupings,
taxonomic differentiations and biostratigraphic usage isprovided for each group. Table 1 provides a summary of
the main Late Miocene to Late Pliocene biostratigraphic
events for species of Discoaster and Minylitha lineages asutilized by BP in the GoM. The stratigraphic use of species
from these groups in the GoM and ODP Leg 154 is discussed from the Upper Pliocene NN19a (1.924Ma) throughthe Middle Miocene (17.692Ma) within NN3. The standard
calcareous zonation (NP/NN Zones) of Martini (1971) isLate Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

Event

Zone
Martini (1971)

Age (Ma)

Discoaster brouweri

HO

NN19A

1.924

Discoaster triradiatus

HO

NN19A

1.924

Discoaster dennei

HO

NN18

Discoaster pentaradiatus

HO

NN17

Discoaster surculus

HO

Discoaster pliostellulus

HO

Discoaster tamalis

191

Error (Ma)Depth
(rmcd)1

926C-6H-5, 64–65cm

0.026

60.27

926C-6H-5, 64–65cm

0.026

60.27

2.024

926B-7H-2, 35–36cm

0.021

62.97

2.327

926A-8H-3, 49–51cm

0.025

72.58

NN16

2.511

926C-8H-4, 21–22cm

0.012

78.23

NN16

2.686

926A-9H-4, 19–20cm

0.027

84.73

HO

NN16

2.752

926C-9H-2, 73–75cm

0.023

86.70

Discoaster variabilis

HO

NN16

2.968

926C-9H-6, 80–82cm

0.022

92.77

Discoaster asymmetricus

INC

NN16

3.019

926A-10H-3, 64–66cm

0.026

94.15

Discoaster tamalis

INC

NN16

3.019

926A-10H-3, 64–66cm

0.026

94.15

Discoaster toralus

HO

NN15

4.085

926B-13H-2, 28–29cm

0.016

127.53

Discoaster pansus

HRO

NN15

4.244

926C-13H-3, 93–94cm

0.023

133.39

Discoaster neorectus

HRO

NN11b

6.445

926B-18H-4, 73–74cm

0.022

184.27

Discoaster subsurculus

HO

NN11b

6.457

926B-18H-4, 97–98cm

0.012

184.51

Taxon

Discoaster pseudovariabilisHole-Core-Sec-Interval

HRO/HO

NN11b

6.457

926B-18H-4, 97–98cm

0.012

184.51

Discoaster extensus

HO

NN11b

6.457

926B-18H-4, 97–98cm

0.012

184.51

Discoaster calcaris

HO

NN11b

6.801

926C-18H-7, 16–17cm

0.022

190.65

Discoaster loeblichii

HO

NN11b

6.821

926C-19H-1, 103–104cm

0.020

190.87

Discoaster icarus

HRO

NN11b

6.832

926C-19H-1, 121–122cm

0.011

191.05

Discoaster neohamatus

HO

NN11b

7.086

926B-19H-4, 91–92cm

0.021

195.25Minylitha convallis

HO

NN11b

7.265

926B-19H-5, 124–125

0.010

197.08Discoaster pachyloeblichii

HO

NN11b

7.332

926B-19H-6, 85–86cm

0.027

198.19

Discoaster breviloeblichii

HO

NN11b

7.374

926A-20H-2, 134–135cm

0.027

199.82

INC/HRO

NN11a

7.848

926B-20H-5, 10–11cm

0.023

206.79

Discoaster prepent. prepentaradiatus

HO

NN10

8.449

926C-22H-3, 53–54cm

0.015

220.61

Discoaster loeblichii

LO

NN10

8.738

926B-22H-4, 95–96cm

0.024

224.81

Discoaster prepent. plautus

INC/HO

NN10

8.806

926B-22H-5, 49–50cm

0.021

225.85

Discoaster styzenii

HRO/HO

NN10

8.902

926B-22H-6, 25–27cm

0.011

227.12

Discoaster prepent. prepentaradiatus andDiscoaster prepentaradiatus plautus

HCO

NN10

8.929

926A-23H-1, 3.5–5.5cm

0.013

227.61

Discoaster prepent. prepentaradiatus

LCO

NN10

9.095

926A-23H-2, 94.5–96.5cm

0.023

230.02

Discoaster bollii

HO

NN10

9.202

926A-23H-3, 115–117cm

0.018

231.72

Discoaster hamatus (<15)

HO

NN10

9.229

926A-23H-4, 20–22cm

0.018

232.27Minylitha cancellata

HO

NN10

9.326

926A-23H-5, 1–3cm

0.025

233.58Discoaster pentabollii

HO

NN10

9.377

926A-23H-5, 75.5–77.5cm

0.023

234.33

Discoaster hamatus (>15)

HO

NN9

9.451
236.74Minylitha convallis

Discoaster caulifloris

HO

NN9

9.542

926A-23H-7, 17–19cm

0.037

Discoaster hamatus (>15)

HRO

NN9

9.618

926B-23H-5, 36–38cm

0.064

237.44

Discoaster tribollii

HO

NN9

9.618

926B-23H-5, 36–38cm

0.064

237.44

Discoaster bollii

2nd acme/INC

NN9

9.727

926A-24H-2,10–12cm

0.022

239.21

Discoaster hamatus (<15)

INC

NN9

9.727

926A-24H-2,10–12cm

0.022

239.21

Discoaster caulifloris

INC

NN9

9.781

926A-24H-2, 139–141cm

0.021

240.50Discoaster gozoensis

HO

NN9

10.451

926A-25H-1, 72–74cm

0.030

249.08Discoaster exilis

HO

NN9

10.490926A-25H-1, 102–104

0.014

249.38Discoaster bollii

LO

NN9

10.716

926A-25H-3, 47.5–49.5cm

0.016

251.84

Discoaster neohamatus

LO

NN9

10.800926A-25H-3, 147–149cm

0.033

252.83

Discoaster hamatus (>15)

LO

NN9

10.963

926A-25H-5, 44–46cm

0.021

254.80Discoaster hamatus (<15)

LO

NN8

11.509926A-26H-2, 26.5–28.5cm

0.010

262.14

Discoaster exilis

LO

NN4

17.393928B-28H-1, 25–26cm

0.014

272.89

Table 1: Main stratigraphic events for the Pliocene-Late Miocene Discoaster and Minylitha in the Gulf of Mexico
1revised measured composite depth (meters); bold = NN zonal marker

192

Browning et al.

widely used as a reference in the GoM, and taxonomic terminology follows Young et al. (1997).
The BP GNATTS is also correlated to the standard
zonation of Martini (1971) and Okada & Bukry (1980) withsome emendations (Blair et al., this volume; de Kaenel et al.,this volume), and is calibrated to the Astronomically Tuned
Neogene Time Scale 2004 (ATNTS2004) (Lourens et al.,2004). This study uses the same section and material fromwhich the ATNTS2004 and ATNTS2012 (Gradstein et al.,2012) was astronomically tuned to obtain well-calibrated
age estimations of the calcareous nannofossil and foraminifera events.
The general groupings provided in this paper represent informal groupings necessary to provide organizational structure to this work only. These groups include:
Discoaster brouweri Group (Plate 1, Figure 2); Discoasterpentaradiatus - prepentaradiatus Group (Plates 1, 2;
Figure 3); Discoaster surculus Group (Plate 2); Discoasterbollii Group (Plate 3 and 5; Figure 4); Discoaster hamatus
Group (Plate 4; Figure 3); Discoaster loeblichii Group(Plate 4; Figure 5); Discoaster variabilis Group (Plate 5;
Figure 6); and Minylitha convallis Group (Plate 5).
4. Systematic paleontology
4.1 Discoaster brouweri Group(Plate 1; Figure 2)
This group includes simple forms that have long, narrowrays with simple tips and a small central area adorned witha small knob. All but one taxon in this group have rays
that bend proximally (Figure 2). The Discoaster brouweriGroup is fundamental to Upper Pliocene biostratigraphy in
the GoM. We discuss six previously described species:
D. triradiatus, D. tamalis, D. blackstockae, D. asymmetricus, D. brouweri and D. neorectus, and also describe one
new taxon, Discoaster dennei. The extinction of D. brouweri marks the end of this lineage and the top of Zone NN18
globally. Below this extinction, the tops of D. dennei,
D. asymmetricus and D. tamalis are utilized as important
stratigraphic markers in Upper Pliocene Zones NN18–NN16.
Discoaster triradiatus Tan, 1927
Pl. 1, fig. 1
Remarks: Discoaster triradiatus has three strongly
curved, bent rays and a small rounded knob.
Occurrence: In the GoM, the HO of D. triradiatus
occurs at the same stratigraphic horizon marked by the HO
of D. brouweri. This horizon is dated at 1.924Ma in Leg
154 and is coeval in the GoM (Table 1). Discoaster triradiatus ranges from the Upper Miocene (NN9) throughterminal Pliocene (top NN18) in Leg 154 (Figure 2).
Discoaster tamalis Kamptner, 1967
Pl. 1, figs 2–4
1967 Discoaster tamalis Kamptner, p. 166, text-fig. 28
Remarks: Kamptner (1967) designated D. tamalis forasteroliths with four orthogonal, bent rays. The distal side

was described as featureless and sutures are not visible;
however, we have observed both features in well-preserved specimens. We have also observed specimens thatare not orthogonal (Pl. 1, fig. 4).
Occurrence: All three heritage companies have utilized the HO of D. tamalis near the top of Zone NN16.
This event is a coeval stratigraphic horizon in the GoM
and Leg 154 and dated at 2.752Ma (Table 1). The LO of
D. tamalis is coeval in the GoM and Leg 154 within Zone
HHD' bJ0gL, :EG0OL1La i1N Ni*LN i* '\$$$Ii b_jdZ\ZCC&
926B-14H-6, 30–31cm).
Discoaster blackstockae Bukry, 1973c
Pl. 1, fig. 51973 Discoaster blackstockae Bukry, p. 315, pl. 1,
figs. 1–4
Remarks: Bukry (1973c) described D. blackstockae as
a four-rayed species with tapering, non-bifurcate bladelike rays. The distinguishing feature of D. blackstockae isthe oblong central area formed by the non–perpendicularintersection of rays, typically resulting in inter-ray angles
of 60° and 120°. In comparison, the rays of D. tamalis are
orthogonal to slightly asymmetrical.
Occurrence: We have not established a firm stratigraphic range for D. blackstockae in the GoM but provide a rough range of Upper Miocene to Pliocene. In Leg
154, the HO of D. blackstockae was observed within
k01L HHD= i1N Ni*LN i* D\<@>Ii b_jdZ\ZZ<& <C$8]$K]$^
19–20cm); the LO is within Zone NN10 and dated at
8.891Ma (+\0.011; 926B-22H-6, 12–14cm).
Discoaster asymmetricus Gartner, 1969
Pl.1, figs 6–7
1969 Discoaster asymmetricus Gartner. p. 595, pl. 1,
figs. 1–3
Remarks: Gartner (1969) described D. asymmetricus
as a slender, five-rayed species of Discoaster distinguished by its ray asymmetry. The rays of these delicate forms “bend sharply proximally at their tip” likeD. brouweri in form and may possess a small central
knob; they are distinguished by their five rays andasymmetry (Figure 2). The main distinction between
D. asymmetricus and D. astellaris is the characteristic
plain central area of the later, for a detailed description
see Blair et al. (2017) in this volume.
Occurrence: In the GoM, the HO of D. asymmetricus and D. pliostellulus (described herein) marka stratigraphic horizon dated at 2.686Ma (Table 1).
The first downhole increases in D. asymmetricus andD. tamalis mark a GoM stratigraphic horizon within
Zone NN16 which is dated at 3.019Ma (Table 1).
In Leg 154, the LO of D. asymmetricus was dated at=\>=@Ii b_jdZ\ZCD& <C$"]CCK]@^ D@MD$O3a^ G*+ K14
0h+L,'LN i* C\C)$Ii b_jdZ\ZC$& <C$8]>K]@^ <)M<@O3a
i1N G*+ K4 i* C\D$@Ii b_jdZ\ZC$& <C$8]>K])^ DD$M
117cm).

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

EARLY

NN19c CN13b

2.686

CN12b

EARLY

NN15

NN14
NN12b
NN12a

5.5

CN12a

CN11a
CN10c

CN10b
CN10a

7.246

LATE

7.5

NN11a

GoM HO6.445/
HRO
Leg 154

Inc @
3.019

4.666

CN9a

CN8b

Tortonian

MIOCENE

8.0

D. triradiatus

7.0

NN11b CN9b

D. brouweri

Messinian

6.5

D. neorectus

5.932

6.0

2.752

Inc @
3.019

D. tamalis

NN16

2.024

?2.165

D. dennei sp. nov.

CN12c

NN13

5.333

9.0

NN17

1.957

CN11b

5.0

8.5

CN12d

1.924

3.600

4.0
4.5

NN18

1.924

D. asymmetricus

PLIOCENE

3.5

2.58

NN19b

NN19a CN13a

D. blackstockae

2.5

Piacenzian

LATE

2.0

Zanclean

1.80

Gelasian

Okada
Martini & Bukry(1971) (1980)

1.5

3.0

Zone

Epoch/
Stage

MIDDLE

Age
(Ma)

193

NN10

8.891

CN8a

9.5
9.689

10.0
NN9

8.785

D. brouweri Group

CN7b

10.5

NN8

11.5
12.0

10.716

CN7a

11.0

CN6

11.63

M. Serr.

NN7

CN5b

11.017

Overlapping GoM/Leg 154 range
Extended GoM range
Extended Leg 154 range

11.531Figure 2: Range diagram of the Discoaster brouweri Group. Ranges, as well as new ages for the NN (Martini, 1971) and CN (Okada & Bukry, 1980)
zonations, are derived from calibrated ages in ODP Leg 154 core samples as well as the Gulf of Mexico

194

Browning et al.

Discoaster brouweri Tan, 1927, emend. Bramlette &Riedel, 1954
Pl. 1, fig. 81927 Discoaster brouweri Tan (pro parte), p. 415, figs. 8a–b;
non figs. 5–7, 14
1954 Discoaster brouweri Tan, 1927, emend. Bramlette &Riedel, p. 402, fig. 12; text-figs. 3a–b
Remarks: Discoaster brouweri is reserved for specimens with six bent rays. Discoaster braarudii andD. dennei (described below) are both constructed of six
flat rays.
Occurrence: The HO of D. brouweri defines the topof Zone NN18 and is a coeval stratigraphic horizon in the
GoM that has been utilized by all three heritage companies
and dated at 1.924Ma in Leg 154 (Table 1). The LO of
D. brouweri may have some stratigraphic utility in
the GoM where it is observed ranging into the lower
part of Zone NN8; just below the top of the newly
described Discoaster hexapleuros (de Kaenel et al., this'0E)3L& DD\@)DIi _jdZ\ZDDa\ T1 JLI D@'^ *HL J4 gi+
observed stratigraphically higher within Zone NN8i1N Ni*LN i* DD\ZD>Ii b_jdZ\ZZ<& <C$<]C@K]@^ DZ$M
108cm), just above the top of the newly described Discoaster cuspidatus, D. emblematicus and D. ulnatus(de Kaenel et al., this volume; 11.037Ma).
Discoaster dennei Browning & Bergen, sp. nov.
Pl. 1, figs 9–11
Derivation of name: Named in honor of calcareous nannofossil specialist, Richard Denne, from Texas Christian
University.
Diagnosis: A medium to large species of Discoasterwith six straight, flat, tapering rays with pointed to slightly
rounded ray terminations.
Description: Six-rayed Discoaster with long, straight,
tapering rays and a small central area. A small knob ispresent on the proximal side. Holotype size = 12.4μm;
Size = 8 to 15μm.
Remarks: Discoaster dennei was informally known
as Discoaster “A” in the BP scheme. Discoaster dennei isdistinguished from D. brouweri by its flat rays and D. neorectus by its smaller size. Discoaster braarudi, describedby Bukry (1971b) from the Middle Miocene, has a verysmall central area and parallel-sided rays with blunt ray
terminations.
Holotype: Pl. 1, fig. 9Type Locality: ODP Leg 154, Hole 926C, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926C-7H-6, 36–37cm (2.262Ma_jdZ\ZC'a^ k01L HHD=^ 5..L, :EG0OL1L
Occurrence: The HO of D. dennei is coeval in the
GoM and Leg 154 where it is dated at 2.024Ma within
Zone NN18 (Table 1). The LO has not been tracked by
BP or the heritage companies in the GoM, but in Leg
154 it is observed to range from the upper part of Zone
NN11b.

Discoaster neorectus Bukry, 1971aPl. 1, fig. 12
1971a Discoaster neorectus Bukry, p. 316, pl. 4, figs. 6–7
Remarks: Bukry (1971a) described D. neorectus as a“gigantic” 6-rayed species of Discoasters between 20–38#m
across, with simple, sharp ray tips that lack downward
extensions or bifurcations.
Occurrence: The HO of D. neorectus marks aprominent Upper Miocene (NN11b) GoM stratigraphic
horizon in conjunction with the HOs of Discoastersubsurculus and HO (GoM)/HRO (Leg 154) of Discoaster pseudovariabilis; this horizon has been dated at
6.457Ma (Table 1). In Leg 154, the HRO of D. neorectus
is observed slightly younger at 6.445Ma (Table 1). It
should be noted that in Leg 154 spotty occurrences are
0h+L,'LN e0)1IL, *0 @\<)CIi b_jdZ\ZC=& <C$"]D>K]'^
127–128cm).
4.2 Discoaster pentaradiatus prepentaradiatus Group(Plates 1, 2; Figure 3)
This group is characterized by five-rayed species ofDiscoasters with small central areas and long, tapering
rays with broad bifurcations (Figure 3; Tan, 1927; Bramlette & Riedel, 1954). Speciation of this group is basedon birefringence (Bukry & Percival, 1971), ray number (Wei, 2003; this study), and thickness of the broad
bifurcations (Bukry & Percival, 1971; this study). Fourdescribed species and subspecies are discussed in thisgroup: D. pentaradiatus, D. styzenii, D. prepentaradiatus prepentaradiatus and D. extensus. One new species
is described, D. trifolius, as well as one new subspecies,
D. prepentaradiatus plautus. Discoaster extensus has
also been placed within this group for organizational purposes and because it is characterized by broad, symmetric, flaring bifurcations, like the group. The extinction of
D. pentaradiatus at the top of Zone NN17 in the Upper
Pliocene has long been a standard GoM marker. Extinctions of this group in the Late Miocene are useful in
the GoM for the division of Zone NN10 (Figure 3;
D. styzenii, D. prepentpentaradiatus prepentaradiatus,
D. prepentaradiatus plautus).
Discoaster pentaradiatus Tan, 1927, emend.
Bramlette & Riedel, 1954
Pl. 1, fig. 27; Pl. 2, figs 1–2
1927 Discoaster pentaradiatus Tan, p. 416, fig. 14
1954 Discoaster pentaradiatus Tan, 1927, emend. Bramlette & Riedel, pp. 401–402, pl. 39, fig. 11; text-figs. 2a–b
Remarks: There is considerable variation in this species,
including size, ray number, arm length and ray length.
Discoaster pentaradiatus is distinguished from all other5-rayed Neogene species of Discoaster by their faint birefringence in cross-polarized light and segmented nature.
Discoaster pentaradiatus is further distinguished by its
bifurcate rays.

Epoch/Stage
Messinian

6.0

Age
(Ma)

6.5
7.0

Martini(1971)Okada& Bukry(1980)

D. hamatus Group

D. pentaradiatusprepent. Group

6.457
6.801

NN11b CN9b
7.086

Overlapping GoM/Leg 154 range

7.246

Extended Leg 154 range

7.5

10.5
CN7a

11.0
11.5
12.0

10.963

NN8

CN6

NN7

CN5b

11.63

10.20010.80011.01710.282

HRO8.902

9.727

8.902

D. trifolius sp. nov.

LCO-9.095

8.522

D. styzenii

HRO 8.806
HCO-8.929

D. prepent. prepent.

D. calcaris
10.513D. extensus

9.618

D. triuncinus sp. nov.

CN7b

inc @
9.727

9.229

D. bolivariae sp. nov.

NN9

9.451

D. hamatus (>15 um)

10.0

D. hamatus (<15 um)

LATE

9.5

9.229

D. neohamatus

NN10
CN8a

8.449

8.539

CN8b

Tortonian

9.0

MIOCENE

8.5

CN9a

D. prepent. plautus ssp. nov.

NN11a

8.0

9.760

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

11.50915.677

195

Figure 3: Range diagram of the Discoaster hamatus Group and Discoaster pentaradiatus-prepentaradiatus Group for the Late Miocene. Ranges,
as well as new ages for the NN (Martini, 1971) and CN (Okada & Bukry, 1980) zonations, are derived from calibrated ages in ODP Leg 154 coresamples as well as the Gulf of Mexico

Zone

196

Browning et al.

Occurrence: The HO of D. pentaradiatus marks
the top of Zone NN17 and has been utilized by all three
heritage companies in the GoM for decades. This horizon is dated in Leg 154 at 2.327Ma (Table 1). Sporadic
specimens, likely reworked, are observed higher in its+*,i*GI,i.HGO ,i1IL G1 JLI D@' ). *0 D\<$$Ii b_jdZ\ZD=&
926C-6H-4,130–131cm). The LO is observed within NN9
G1 *HL X0I i1N Ni*LN i* <\=')Ii G1 JLI D@' b_jdZ\ZDD&
926A-24H-3,108–110cm), just below the HO (GoM)/
HRO (Leg 154) of Catinaster coalitus (de Kaenel et al.,this volume; 9.826Ma).
Discoaster trifolius Browning & Bergen, sp. nov.
Pl. 1, fig. 13
Derivation of name: From the Latin tri, meaning threeand folius, meaning leafy, leaved
Diagnosis: A three-rayed species of Discoaster having
long, non-birefringent rays with symmetric bifurcations.
Description: A species of Discoaster having threelong rays that are not birefringent. The rays broaden
peripherally to form wide, delicate, symmetric bifurcations. A short distal knob is present in the small central
area. Holotype = 10.0#m
Remarks: Discoaster trifolius is described for threerayed D. prepentaradiatus. Other bifurcate three-rayedspecies of Discoaster are distinguished from D. trifolius
in the following ways: D. tribollii has a high distal stem;
D. triuncinus (described below) has asymmetric bifurcations, and three-rayed D. pentaradiatus are birefringent.
Holotype: Pl. 1, fig. 13
Type Locality: ODP Leg 154, Hole 926A, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926A-23H-4, 54.5–56.5cm
b<\C@$Ii _jdZ\ZC)a^ k01L HHDZ^ 5..L, IG0OL1L
Occurrence: The HO of D. trifolius is coincident
with the HRO (Leg 154)/HO (GoM) of D. styzenii in
3GN]HHDZ i1N Ni*LN i* =\<ZCIi b_jdZ\ZD'& <C$"]CCK]$^
25–27cm) in Leg 154. The LO is in upper Zone NN9 andNi*LN i* <\>$ZIi G1 JLI D@' b_jdZ\ZCD& <C$<]C'K]C^
91–93cm). The range of this species is not well establishedin the GoM.
Discoaster styzenii (Wei, 2003) Browning & Bergen,
emend.
Pl. 1, figs 14–16
2003 Discoaster styzenii Wei, p. 21, pl. 2, figs. 5–8
Emended description: A species of Discoaster having
four long rays that are not birefringent. The rays taper andthen broaden peripherally to form symmetric bifurcations.
The bifurcations are thin and broad. The angle formed by
the rays is variable; they may be arranged in a symmetricor asymmetric fashion. A short distal knob is present in thesmall central area. Size range = 8.1–10.4#m (11 measured
specimens)
Remarks: Discoaster styzenii is a four-rayed variant of D. prepentaradiatus. The short description of thisspecies by Wei (2003) is insufficient to differentiate itfrom other four-rayed Neogene species of Discoaster withbifurcations. The emendation also includes specimens
with orthogonal and symmetric rays. Discoaster bolivariae (described herein) has asymmetric bifurcations,and D. quadribollii (described herein) has a large and highdistal stem. Four-rayed D. variabilis have thicker arms
and bifurcations.
Occurrence: This species is found in deep-water
GoM, and BP has long-utilized its extinction within Zone
NN10 as a stratigraphic horizon. The HRO of D. styzenii
is observed in mid-Zone NN10 and dated at 8.902Ma in
Leg 154 (Table 1) and considered equivalent to the HO in
the GoM. In Leg 154 younger, sporadic occurrences are
0h+L,'LN *0 =\@CCIi b_jdZ\ZD>& <C$8]CCK]'^ >M=O3a\
The LO has not been established for this species in the
GoM but was observed in ODP Leg 154 (upper Zone
HH<a *0 ,i1IL K,03 <\>C>Ii b_jdZ\ZCC& <C$<]C'K]C^
10–12cm).
Discoaster prepentaradiatus Bukry & Percival, 1971
prepentaradiatus Browning & Bergen ssp. nov.
Pl. 1, figs 23–26
1971 Discoaster prepentaradiatus Bukry & Percival (proparte), p. 129, pl. 3, fig. 6; non fig. 7
Remarks: Bukry & Percival (1971) mentioned thin bifurcations in their description of this species. The bifurcations of the holotype are also delicate. It is likely that mostof the delicate bifurcation is missing on the holotype.
The species is further characterized by being planar andnon-birefringent. The small central area has a small stellate knob, although no knob is mentioned in the description. Holotype = 10.5#m; Size = 9–20#m
Discoaster prepentaradiatus prepentaradiatus is differentiated from D. pentaradiatus, another five-rayed Neogene species of Discoaster with delicate bifurcations, as it
is only faintly birefringent. Discoaster prepentaradiatus
plautus (described below) has broad, thick bifurcations.
Discoaster hamatus has asymmetric, curved bifurcations and significant size variation. Small specimens of
D. hamatus are difficult to distinguish from small D. prepentaradiatus prepentaradiatus with the light microscope
when the thin bifurcations of the latter are broken.
Occurrence: The HO of D. prepentaradiatus prepentaradiatus, the thin bifurcation variety, is dated at 8.449Ma
in Leg 154 (Table 1) and represents the extinction of theentire D. prepentaradiatus group (3–5 rays) in the Upper
Miocene uppermost Zone NN10 (Figure 3). The LO of thespecies is within Zone NN9 in the GoM and ODP Leg
D@' i1N G+ Ni*LN i* DZ\C=CIi b_[dZ\ZD'& <C$<]C'K]>^
11–13cm). The acme (HCO and LCO) of the species (bothD. prepentaradiatus prepentaradiatus and D. prepentaradiatus plautus; described below) is not often observed
in deep-water GoM wells because of a regional unconformity often associated with the HOs of D. bollii and
D. styzenii (9.202Ma; Table 1). This acme lies in mid-Zone

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

NN10 within the Leg 154 section, spanning 9.095Ma(LCO D. prepentaradiatus prepentaradiatus) to 8.929Ma(HCO D. prepentaradiatus prepentaradiatus; Table 1).
Discoaster prepentaradiatus Bukry & Percival, 1971
plautus Browning & Bergen, ssp. nov.
Pl. 1, figs 17–19
1971 Discoaster prepentaradiatus Bukry & Percival(pro parte), p. 129, pl. 3, fig. 7; non fig. 6
Derivation of name: From the Latin plautus, meaning
broad, flat
Diagnosis: A subspecies of Discoaster prepentaradiatus with thick, broad bifurcations
Description: A large species of Discoaster with fivelong, tapering rays and broad, thick bifurcations. The surface of the thick ray terminations appears “lipped,” smooth
and arcuate upon focus. Upon refocus, the juncture of thebifurcation appears notched. The rays are arranged symmetrically or asymmetrically; proximal ridges may run
from the center down the median of the rays. The center isrelatively large for the species, being about 1/4 to 1/5 thesize of the specimen. A small central knob is present but
may occupy up to 1.2 the size of the central area. Specimens are non-birefringent. Size = 10.4–12.5μm (six measured specimens)
Remarks: Discoaster extensus and D. variabilis haverare five-rayed variants that can be difficult to distinguishfrom D. prepentaradiatus plautus. In D. extensus, therays are not thickened or “lipped” at their ends, although
this surface is arcuate and has a distinct ‘crescent moon’like appearance. The ray terminations of D. variabilis do
not have this smooth arcuate appearance but are notched.
The generally smaller D. prepent. prepentaradiatus has
narrow, thin bifurcations. The extinctions of the two
subspecies of D. prepentaradiatus are stratigraphicallyclose, but their stratigraphic separation has been utilized
as distinct markers in GoM wells by BP for over a quarter
century.
Holotype: Pl. 1, fig. 17
Type Locality: ODP Leg 154, Hole 926A, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926A-23H-2, 72.5–74.5cm
b<\Z>@Ii _[dZ\ZCZa^ k01L HHDZ^ 5..L, IG0OL1L
Occurrence: The HO of this subspecies is a marker in
the GoM, and a coeval increase in ODP Leg 154 is dated
at 8.806Ma (Table 1) and is slightly older than Discoaster
prepent. prepentaradiatus (8.449Ma; Table 1). In Leg
154, the HO of D. prepentaradiatus plautus is observede0)1IL, i* =\@)<Ii b_[dZ\ZD<& <C$8]CCK]'^ )=M)<O3a\
The LO is observed within NN9 in Leg154 and dated at
DZ\CZZIi b_[dZ\Z)'& <C$<]C'K]$^ $$\@M$=\@O3a\
Discoaster extensus Hay, 1967
Pl. 1, figs 20–22
1967 Discoaster extensus Hay, in Hay, Mohler, Roth, Schmidt& Boudreaux; p. 451, pl. 3, figs. 10, 12, pl. 4, figs. 1–2

197

Remarks: The original description stresses the peripheral flare of the rays and bifurcations that curve sharply
downward at the point of bifurcation. Upon focus, thebifurcations appear both notched at the level of the ray
and arcuate at their tips, having a ‘crescent-moon shape’appearance between the tips (Figure 3). Hay et al. (1967)
also described rays of moderate length and breadth, asmall central area (<1/2 the total diameter) lacking sculpture, and a size range of 11–13#m. The size range of thisspecies is extended to 8–13#m, and very rare three tofive-rayed forms have been observed. One specimen has
rays whose length are about equal to the central area diameter (Pl. 1, fig. 20), whereas the remaining specimens all
have rays that are at least 1.5 times longer the central area
(Pl. 1, figs 21–22). A small central knob is present, andmany specimens have medial ridges radiating from thecenter down the length of the rays. Discoaster loeblichii
also has bifurcations that bend downward, but they bifurcate asymmetrically (Figure 5).
Occurrence: The HO of D. extensus marks a prominent Upper Miocene horizon (mid-Zone NN11b) in the
GoM, along with the HOs of D. neorectus, D. pseudovariabilis and D. subsurculus. This horizon and the HO
of D. extensus is dated at 6.457Ma (Table 1) in Leg154.
The LO has not been used as a marker in the GoM but wasobserved in Leg154 to range into Zone NN4 and dated at
D@\$>>Ii b_[dZ\ZCD& <C@6])>K]C^ D)ZMD)DO3a\4.3 Discoaster surculus Group (Plate 2)
The Discoaster surculus Group contains Late Pliocene toLate Miocene species of Discoasters with trifurcate bifurcations (Martini & Bramlette, 1963). Changes in the shapeand orientation of the middle spur in the trifurcate bifurcation are used to distinguish species and subspecies of thisgroup (Martini & Bramlette, 1963; Gartner, 1967; Martini& Worsley, 1971). The forms D. toralus and D. pliostellulus are included in this group for this paper, but they do nothave trifurcate bifurcations and, instead, are characterized
by rays with blunted ends. In the GoM, D. subsurculus
and D. pseudovariabilis have extinctions at the same levelwithin the Upper Miocene (Zone NN11b). Both species
possess complex middle spurs. The last form in this group,
D. surculus, has a simple, bright, bulb-shaped spur. Its
extinction is a standard Upper Pliocene GoM marker anddefines the top of Zone NN16. Four species are discussed
from this group: D. surculus, D. subsurculus, D. pseudovariabilis and D. toralus. One new species is described,
D. pliostellulus.
Discoaster surculus Martini & Bramlette, 1963
Pl. 2, figs 3–6, 8
1963 Discoaster surculus Martini & Bramlette, p. 854,
pl. 104, figs. 10–12
Remarks: Martini & Bramlette (1963) reserved D. surculus for trifurcate species of Discoasters with simple,
bright, bulb-shaped spurs and six or, rarely, fewer rays.

198

Browning et al.

We have not observed any stratigraphic significance to thethree- to five-rayed variants.
Occurrence: The HO of D. surculus marks the topof Zone NN16 and a coeval stratigraphic horizon in the
GoM and Leg 154 utilized by all three heritage companies. In ODP Leg 154, the HO is dated at 2.511Ma(Table 1). The LRO of D. surculus is dated at 7.870Ma
b_[dZ\ZCZ& <C$"]CZK]@^ '<M@ZO3a i1N J4 G+ Ni*LN i*=\C$DIi b_[dZ\Z)D& <C$"]CDK]@^ DC>MDC=O3a G1 JLI
154; neither has been used as a stratigraphic marker in
the GoM.
Discoaster subsurculus Gartner, 1967
Pl. 2, fig. 71967 Discoaster subsurculus Gartner, p. 3, pl. 5, figs.
1a–b, 2a–b
Remarks: Discoaster subsurculus has trifurcate ray terminations. The lateral branches of the trifurcation arebroad; the protrusion between these branches is describedas long and “knob-like” and often bends proximally.
The proximal bend of the long central protrusion may
have the appearance of a downward bending ‘claw’ in
well-preserved specimens. Discoaster subsurculus is distinguished from the other two species with trifurcate rays,
D. surculus and D. pseudovariabilis, by its long “knoblike” bending protrusion, where the central spur appears
as a simple, bright, bulb-shaped spur in D. surculus andas “tongue-like,” paired elements in D. pseudovariabilis.
Occurrence: The HO of D. subsurculus marks aprominent upper Miocene (NN11b) GoM stratigraphic
horizon, along with the HOs of D. pseudovariabilis andD. extensus, and is dated at 6.457Ma in Leg 154 (Table 1).
Discoaster pseudovariabilis Martini & Worsley, 1971
Pl. 2 figs 9–14
1971 Discoaster pseudovariabilis Martini & Worsley (proparte), p. 1500, pl. 3, figs. 2–5; non pl. 3, figs. 6–8
Remarks: Discoaster pseudovariabilis has trifurcate rayterminations. Martini & Worsley (1971) described theradial portion of this trifurcation as a “tongue-like projection”. Discoaster surculus and D. subsurculus are also
trifurcate, but their radial projections are not “tongue-like”
or composed of paired elements.
Occurrence: The HO of D. pseudovariabilis marks
a prominent Upper Miocene (NN11b) GoM stratigraphic
horizon along with the HOs of D. subsurculus and D.
extensus. This horizon is dated at 6.457Ma in Leg 154
and represents the HRO of D. pseudovariabilis in Leg
154 (Table 1). Sporadic specimens of D. pseudovariabilis
where observed stratigraphically younger in Leg 154 to$\Z'DIi b_[dZ\ZD>& <C$8]D>K]'^ D<MCZO3a\Discoaster toralus Ellis, Lohman & Wray, 1972
Pl. 2, figs 15–16
1972 Discoaster toralus Ellis, Lohman & Wray, p. 53, pl.
16, figs. 2–6

Remarks: Discoaster toralus has a relatively large central
area and parallel-sided rays with flat to rounded terminations. It is characterized by the thick proximal ridges thatradiate from the center down the rays and the inter-ray“webbing”. Discoaster intercalaris and D. pliostellulus
are other six-rayed forms with large, ornamented central
areas, but their rays are tapered.
Occurrence: The HO of D. toralus is tied to a GoM
stratigraphic horizon in zone NN15 marked by the HO
of Helicosphaera zeta and dated in Leg 154 at 4.069Ma(Boesiger et al., 2017; this volume). In Leg 154 the HO
of D. toralus gi+ 0h+L,'LN i* '\Z=@Ii b_[dZ\ZD>& <C$"]
13H-2, 28–29cm).
Discoaster pliostellulus Browning & Bergen, sp. nov.
Pl. 2, figs 17–19
Derivation of name: From the Greek pleion, meaning
more, and stellula (diminutive), meaning star
Diagnosis: A six-rayed species of Discoaster having
short tapered rays
Description: An asterolith with a large central areaand six, short tapering rays. The ray terminations arerounded, flat or slightly notched. Narrow, thick ridges
extend from a prominent stellate central stem.
Remarks: Discoaster pliostellulus is described for
Pliocene forms like the Miocene D. stellulus. In Leg 154,
the ranges of these two species are separated by approximately 6My and Discoaster toralus ranges into the Lower
Pliocene. It has thick radial ridges, but it differs fromD. pliostellulus by having parallel-sided rays and inter-ray
webbing.
Holotype: Pl. 2, fig. 19
Type Locality: ODP Leg 154, Hole 926A, Ceará Rise
western equatorial Atlantic
Type Level: Sample 926-10H-2, 144–145cm
bC\<<)Ii _jdZ\ZC$a^ k01L HHD$^ IGNNEL :EG0OL1L
Occurrence: The HO of D. pliostellulus is along-standing BP GoM marker in the Middle Pliocene(uppermost Zone NN16) and dated at 2.686Ma Leg 154(Table 1). In Leg 154, the LO is observed within the Lower
Pliocene (lowermost Zone NN16) and dated at 3.707Ma
b_[dZ\ZCZ& <C$<]DCK])^ >)M>'O3a\
4.4 Discoaster bollii Group(Plates 3 and 5; Figure 4)
The Discoaster bollii Group is characterized by medium
to large species of Discoasters with a thick, high knob
in the central area and delicate bifurcations (Martini &Bramlette, 1963). The thick stem yields a ‘shadow’- like,dark ring around the base of the stem. This group can be
split into stratigraphically-useful taxa based on form andray number (Wei, 2003; this study, Figure 4). Three ofthe species included in this group for this paper, D. exilis,
D. gozoensis and D. decorus, do not have characteristics
identical to those of the Discoaster bollii Group. Thesetaxa possess delicate bifurcations like the group but do notLate Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

Zone
Okada
Martini & Bukry(1971) (1980)

CN8b

9.0

NN10

D. bollii Group

HO3.746

CN8a

9.202

10.5

CN7b
NN9

10.451

10.490

CN7a

11.0
11.5

NN8

CN6

NN7

CN5b

NN6

CN5a

D. bollii

inc9.781

D. decorus

LATE

10.0

Tortonian

9.542

D. pentabollii

9.377

9.5

inc/acme9.727

10.200D. tribollii sp. nov.

Epoch/
Stage

D. quadribollii sp. nov.

Age
(Ma)
8.5

199

9.618

10.08210.716

11.63

13.82

NN5

CN4

Langhian

14.5
15.0

D. exilis

14.0

13.240D. gozoensis

13.5

MIDDLE

13.0

MIOCENE

12.5

15.5
15.97

16.0

D. caulifloris sp. nov.

Serravallian

12.0

15.938NN4CN3Burdigalian

17.0

EARLY

16.5

Overlapping GoM/Leg 154 range

17.5
18.0

17.393

NN3

CN2

Extended GoM range

17.692

Figure 4: Range diagram of the Discoaster bollii Group for the Miocene. Ranges, as well as new ages for the NN (Martini, 1971) and CN (Okada &Bukry, 1980) zonations, are derived from calibrated ages in ODP Leg 154 core samples as well as the Gulf of Mexico

200

Browning et al.

have a thick, high central knob. They are placed within thisgroup for the convenience of this paper only because thesetaxa have delicate bifurcations like the group (Figure 4).
The holotypes and taxa illustrated here were examined andphotographed from material in the original Bolli collection (Bolli, 1957) sampled by H.M. Bolli in Trinidad. Fivedescribed taxa from this group are discussed: D. bollii,
D. pentabollii, D. exilis, D. gozoensis and D. decorus.
Three new species are described: D. tribollii, D. quadribollii, and D. caulifloris. The extinction of D. bollii has
been long-used as GoM marker in the Upper Miocene
Zone NN10. The use of the HO, acme or increase, and LOof this group provide stratigraphically useful events within
Zones NN10 and NN9 in the GoM (Figure 4).
Discoaster bollii Martini & Bramlette, 1963
Pl. 3, figs 10–16
1963 Discoaster bollii Martini & Bramlette (pro parte), p.
851, pl. 105, fig. 1; non figs. 2–4, 7
Remarks: Martini & Bramlette (1963) described D. bollii
as five-and-six rayed forms and illustrated specimens withvarying arm lengths. The holotype has relatively longarms with a free ray length to center ratio of 0.71. We distinguish between forms with long (Plate 3, figures 10–13)
and short arms (Plate 3, figures 14–16) but they do show
identical ranges (Figure 4). The forms with short arms
have a free ray length to central area ratios between 0.29
and 0.58. The original description is 10–14#m in size. Thistaxon is characterized on one side by a prominent large
stellate stem with a height great enough as to appear in
the light microscope as a bright central feature surrounded
by a dark, ‘shadow’- like ring at the base of the stem. The
other side possesses a less prominent stem.
Occurrence: The extinction of D. bollii provides
an important biostratigraphic event in the Upper Miocene (NN10), which has been used in the GoM for
decades and is dated in Leg 154 at 9.202Ma (Table 1;
Figure 4). The 2nd acme of D. bollii, along with the firstincrease of D. hamatus (<15), is used as a stratigraphic
event within Zone NN9 in the GoM and is dated at Leg
154 as 9.727Ma (Table 1). This event in Leg 154 wasobserved as an increase in D. bollii, rather than an acme
as observed in the GoM (Table 1). In the GoM, there isa smaller increase of D. bollii that is stratigraphically
younger than the event represented by the dual increasein D. bollii and D. hamatus at 9.727Ma. The base of
D. bollii has been observed as coeval in the GoM andLeg 154 within Zone NN9 and is dated at 10.716Ma in
Leg 154 (Table 1).
Discoaster tribollii Browning & Bergen, sp. nov.
Pl. 3, figs 1–2
Derivation of name: From the Latin tri, meaning thriceand bollii, named in honor of Dr. Hans Bolli
Diagnosis: A Discoaster with three short, tapering
rays with narrow bifurcations and a large stellate stem.

Description: A medium to large species of Discoasterwith three long, tapering rays and short, narrow bifurcations. Discoaster tribollii is characterized by a large, stellate distal stem with a height great enough as to appear in
the light microscope as bright central feature surrounded
by a dark, ‘shadow’- like ring at the base of the stem. The
proximal side possesses a less prominent stem. Holotype =8#m; the other specimen presented here is 11.4#m, assuming asymmetry.
Remarks: This taxon is distinguished from otherthree-rayed Neogene species of Discoasters by its highdistal stem and delicate bifurcations. It is distinguishedfrom other species of the Discoaster bollii group by its
ray number.
Holotype: Pl. 3, fig. 1
Type Locality: Bolli Collection, Trinidad
Type Level: KR23425, Zone NN9, Upper Miocene
Occurrence: The HO of D. tribollii is near upper
Zone NN9 in the GoM and Leg 154, where it was dated at
9.618Ma (Table 1). Its lowest occurrence in Leg 154 was
0h+L,'LN G1 k01L HH< bDZ\Z=CIi _[dZ\ZC=& <C$<]C'K]@^
107–109cm) but hasn’t been well established in the GoM.
Discoaster quadribollii Browning & Bergen, sp. nov.
Pl. 3, figs 3–5
Derivation of name: From the Latin quadri, meaning
four and bollii, named in honor of Dr. Hans Bolli
Diagnosis: A species of Discoaster that has four short,tapering rays with bifurcations and a large stellate stem.
Description: A medium to large Discoaster with four
tapering rays with bifurcations. The rays may or may not
be arranged orthogonally. The species is characterized
by a large stellate stem with height great enough as toappear in the light microscope as bright central featuresurrounded by a dark, ‘shadow’- like ring at the base of
the stem. The proximal side possesses a less prominent
stem. Holotype = 10#m
Remarks: Discoaster quadribollii is distinguishedfrom other four-rayed Neogene species of Discoaster by
its high distal stem and bifurcations. It is distinguishedfrom other species of the Discoaster bollii group by its
four arms.
Holotype: Pl. 3, figs 3–5Type Locality: Bolli Collection, Trinidad
Type Level: KR23425, Globorotalia menardi Zone,
Zone NN9, Upper Miocene
Occurrence: The holotype for D. quadribollii wastaken from lectotype material for D. bollii used by Martini& Bramlette (1963). We do not have a range for this taxon
as it is extremely rare.
Discoaster pentabollii Wei, 2003
Pl. 3, figs 6–9
2003 Discoaster pentabollii Wei, p. 20 pl. 1, figs. 13–14
Remarks: Wei (2003) described this taxon as having five bifurcate rays with a large stellate stem andLate Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

relatively large central area. The two specimens illustrated by Wei (2003) have central areas approximately
1/3 the total size of the specimen. We have seen ratiosof 1/4 to almost 1/2 of the total size of the specimen.
We have also noticed the variation in the width of thestem, though all specimens have very high stems thatappear to cast a shadow at the base of the stem, which
is characteristic of the group. Discoaster pentabollii isdistinguished from other species in the group by the
number of rays. It also has tapering rays and short, narrow bifurcations. The size for specimens cited herein is
7.2–12.0#m.
Occurrence: In the GoM the HO of D. pentabollii isnear the base of Zone NN10 and is dated in Leg 154 at
9.377Ma (Table 1). Its lowest occurrence in Leg 154 is
G1 k01L HH< bDZ\CZZIi _[dZ\Z)'& <C$<]C'K]$^ $$\@M
68.5cm); however, its base is not well established in the
GoM but has been observed into Zone NN8.
Discoaster caulifloris Browning & Bergen, sp. nov.
Pl. 3, figs 17–21
Derivation of name: From the Latin cauli, meaning stem
and from L. floris, meaning blossom
Diagnosis: A species of Discoaster that has six longrays with wide bifurcations and a large stellate stem.
Description: A medium to large species of Discoasterwith six long rays, which are parallel-sided to slightly
tapering. The bifurcations are wide and broad, like thosepossessed by D. variabilis. The central area is approximately 1/3 the size of the specimen. The large stellate stemtakes up approximately 1/2 of the central area with heightgreat enough as to appear in the light microscope as brightcentral feature surrounded by a dark ‘shadow’- like ring at
the base of the stem. Size = 6–12.5#m
Remarks: Discoaster caulifloris is characterized by
its wide bifurcations and roughly parallel-sided arms. In
contrast, D. bollii has strongly tapering rays and delicate,narrow bifurcations.
Holotype: Pl. 3, fig. 20
Type Locality: ODP Leg 154, Hole 926A, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926A-24X-3, 108–110cm
b<\=')Ii _[dZ\ZDDa^ k01L HH<^ 5..L, IG0OL1L
Occurrence: The HO of D caulifloris is in Zone
NN9 in the GoM and Leg 154, where it is dated at
9.542Ma (Table 1). Its lowest occurrence in Leg 154,i1IL+ G1*0 k01L HH' bD@\<)=Ii _[dZ\ZCZ& <C@8])=K])^
135–136cm). Its base is not well established in the GoM
but is within the lower Middle Miocene. A stratigraphically useful increase in D. caulifloris is coeval in the GoM
and Leg 154 and dated at 9.781Ma (Table 1).
Discoaster exilis Martini & Bramlette, 1963
Pl. 3, figs 22–26
1963 Discoaster exilis Martini & Bramlette, p. 852 pl. l04,
figs. 1–3

201

Remarks: Martini & Bramlette (1963) described D. exilis
as a six-rayed species of Discoaster with a small centralarea, small stellate knob and long, slender rays that taper
outward. The distinguishing characteristic of D. exilis
is the “faint ridges extending radially to one side of themedian line” along the ray (Figure 4). These faint ridges
extend from the center and curve along the side of therays as clearly illustrated in the holotype (fig. 1). It is
this curvature of the sutures down the side of the raythat distinguishes D. exilis from D. gozoensis, where
the suture is linear and runs down the center of the rays
(Figure 4). This very specific morphotypic distinction
has long-been used by GoM workers and heritage companies. In the GoM, overgrowth can prevent preservation of this feature.
Occurrence: The HO of D. exilis is a key marker
utilized by the three heritage companies in the GoM(lower Zone NN9) and has been dated in Leg 154 as
10.490Ma (Table 1). Its LO is a marker in the GoM and isobserved slightly older than the LCO of S. heteromorphus(17.383Ma; Bergen et al., 2017; this volume) and dated in
Leg 154 at 17.393Ma (Table 1; NN4).
Discoaster gozoensis Hojjatzadeh, 1978
Pl. 3, figs 27–30
1978 Discoaster gozoensis Hojjatzadeh, p. 10 pl. 3, figs. 2, 3
Remarks: The original description of D. gozoensis
mentions ridges which radiate from the center along themedian line of each ray, and originally illustrated specimens have six tapered rays with apparent narrow bifurcations (Hojjatzadeh, 1978). We separate D. gozoensis from
D. exilis by the linear ridges that radiate down the medianline of each ray (Figure 4), as opposed to their curved
nature in D. exilis. In the BP nomenclature, this was previously referred to as Discoaster cf. exilis.
Occurrence: In the GoM, the HO of D. gozoensis isobserved just above D. exilis in mid-Zone NN9 and dated
in Leg 154 at 10.451Ma (Table 1). In the GoM, the LO isobserved below the base of D. exilis (17.393Ma, Leg 154)
G1 k01L HH) i1N Ni*LN i* D>\$<CIi b_[dZ\ZCD& <C="]
28-4, 135–136cm).
Discoaster decorus (Bukry, 1971b) Bukry, 1973bPl. 5, fig. 10
1971b Discoaster variabilis decorus Bukry, p. 48, pl. 3,
figs. 5, 6
1973 Discoaster decorus (Bukry, 1971), p. 677, pl. 2,
figs. 8, 9; pl. 4, fig. 11
Remarks: Bukryi (1971b) described this as a subspeciesof Discoaster variabilis, distinguishing it by its narrowbifurcations and consistently larger size, giving a size
range of 15–27#m. In addition, we distinguish D. decorusby both its large size and ‘notches’ in the narrow bifurcations.
Occurrence: In the GoM, the HO of D. decorus isloosely associated with the HO of R. pseudoumbilicus

202

Browning et al.

(uppermost NN15), and both are dated at 3.746Ma in
JLI D@' b_jdZ\ZD<& <C$<]DC])^ D)'MD)@O3a\ 0.0,iNGO
reworked specimens of D. decorus were observed stratiI,i.HGOiEEe e0)1IL, G1 JLI D@' ). *0 )\@)DIi b_[dZ\ZDC&
926C-11-3, 55–56cm).
4.5 Discoaster hamatus Group(Plate 4; Figure 3)
Martini & Bramlette (1963) originally described D. hamatus as forms with three to seven rays that are “long, somewhat curved, and turn sharply clockwise and downward
toward at the end.” In well-preserved specimens, the rayterminations have a distinguishable split in which one of
the ray bifurcation turns downward. Next to this downward termination is a small, straight spur which leads tothe split-nature of the asymmetric bifurcations (Figure 3).
We restrict the name D. hamatus to forms with five rays
and use D. neohamatus and D. calcaris for forms with six
rays; two new species are described for three- and fourrayed variants, D. triuncinus and D. bolivariae, respectively. Two species in this group are emended, D. hamatusand D. neohamatus. The total range of D. hamatus (>15)
defines Zone NN9 (Figure 3). In addition, small forms(less than 15μm) of D. hamatus have also been used by
BP as a distinct stratigraphic event in the base of Zone
NN10 in the GoM.
Discoaster triuncinus Browning & Bergen, sp. nov.
Pl. 4, figs 1–3
1984 Eu-discoaster hamatus (Martini & Bramlette) Theodoridis (pro parte), p. 174–175, pl. 37, fig. 7; non. pl. 12
fig. 13; non. pl. 37, figs. 4–6
Derivation of name: From the Latin tri, meaning three;
and uncinus, meaning hook
Diagnosis: A three-rayed species of Discoaster withlong arms that sharply bend downward near their terminations with an accompanying small, straight spur.
Description: Discoaster triuncinus varies in size
from approximately 8–12#m (measurements of three
specimens). This taxon is the three-rayed variant of
D. hamatus. Like D. hamatus, the long arms of thistaxon bend sharply downward near the terminations at
which point a small straight spur forms a small asymmetric bifurcation. Also, like D. hamatus, this straightspur is likely to be observed only in well-preserved
specimens.
Remarks: The distinct downward bending bifurcations with accompanying spurs distinguish D. triuncinus
from D. trifolius, which has delicate symmetric bifurcations, and from D. tribollii, which has a high stem andsmall equal bifurcations.
Holotype: Pl. 4, figs 1–2Type Locality: ODP Leg 154, Hole 926A, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926A-24X-3, 20.5–22.5cm
b<\=Z)Ii _[dZ\ZC)a^ k01L HH<^ 5..L, IG0OL1L

Occurrence: There is uncertainty in the exact range
because of its spotty and rare occurrences, but it has been
0h+L,'LN K,03 k01L HH= bDD\ZD>Ii _[dZ\ZZ<& <C$<]
C@K]@^ DZ$MDZ=O3a ] HHDZ b<\CC<Ii _[dZ\ZC>& <C$<]
23H-4, 20–22cm) in Leg 154. In the GoM, the HO has
been observed to be associated with the HO of C. coalitus(>10) and an increase in C. coalitus dated at 10.403Ma
b_[dZ\ZZ=& <C$<]C@K]D^ )@M)>O3a G1 JLI D@' bNLSiL1LE
et al., 2017; this volume).
Discoaster bolivariae Browning & Bergen, sp. nov.
Pl. 4, figs 4, 6
Derivation of name: Named in honor of foraminifera
specialist, Maria Auxiliadora Bolivar from BP
Diagnosis: A four-rayed species of Discoaster that haslong arms that sharply bend downward near their terminations with an accompanying small, straight spur.
Description: This is a four-rayed variant of D. hamatus and likewise has long arms and asymmetric bifurcations characterized by a sharp downward bend near
the terminations with an accompanying small, straightspur. This taxon is medium to large in size; specimens range from 8–12#m and may have a small distal
knob.
Remarks: Discoaster bolivariae is distinct from otherfour-rayed species of Discoasters by the nature of its ray
terminations. It is distinguished from the other membersof the D. hamatus group by its ray number.
Holotype: Pl. 4, fig. 6
Type Locality: Bolli Collection, Trinidad
Type Level: KR23425, Zone NN9, Upper Miocene
Occurrence: There is uncertainty in the range becauseof spotty and rare occurrences. The HO of D. bolivariae
has been observed within Zone NN9 in Trinidad.
Discoaster hamatus (Martini & Bramlette, 1963)
Browning & Bergen, emend.
Pl. 4, figs 5, 7–8, 10
1963 Discoaster hamatus Martini & Bramlette, p. 852–
853, pl. 105, figs. 8,10,11
Emended Diagnosis: A five-rayed species of Discoasterwith long arms that sharply bend downward near their terminations with an accompanying small, straight spur.
Remarks: This taxon is emended to restrict it to
five-rayed forms. The original description mentioned asize range of 16–20#m. This criterion is critical because
Zone NN9 is defined by the total range of D. hamatus.
The authors have found its total range to be strongly
size-dependent (Figure 3). We have chosen to use specimens of D. hamatus greater than 15#m to delineate thelimits of Zone NN9. The smaller forms (less than 15#m)
range stratigraphically higher and lower. These smaller
forms of D. hamatus can also be difficult to distinguishbetween five-rayed forms of D. prepentaradiatus andD. bellus in poorly preserved materials where examination of ray terminations is difficult.

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

Occurrence: The HO and HRO of D. hamatus (>15)
have been dated as 9.451Ma and 9.618Ma, respectively, inLeg 154. The HO in GoM calibrates to HRO in Leg 154
dated at 9.618Ma. The total range of D. hamatus (>15) is
10.963Ma to 9.451Ma (Table 1) and is used for the boundaries of Zone NN9 (Figure 3). The HO of the smaller variant of D. hamatus (<15) is dated in Leg 154 at 9.229Ma(Table 1). Isolated occurrences, likely reworked, have been
noted in the Leg 154 material into Zone NN11b (7.402Ma_jdZ\ZD>& <C$<]CZK])^ C'MC@O3a\ T1 *HL X0I^ *HL J4 0K
D. hamatus (<15), dated at 11.509Ma in Leg 154 (Table 1),
is associated with the top of D. kugleri (deKaenel et al.,2017).
Discoaster neohamatus (Bukry & Bramlette, 1969)
Browning & Bergen, emend.
Pl. 4, fig. 11
1969 Discoaster neohamatus Bukry & Bramlette, p. 133,
pl. 1, figs. 4–5
Emended Diagnosis: A six-rayed species of Discoasterwith long arms that are bent sharply downward near theirterminations and have an accompanying small, straightspur.
Remarks: Bukry & Bramlette (1969) mentioned thatD. neohamatus possesses six long slender rays whichcurve consistently in one direction and has no central area
ornamentation. We believe the two specimens illustrated
by Bukry & Bramlette (1969) are overgrown and haveemended the description to include 1) that the ray ends
possess two delicate bifurcations, in which one curves andbends in one direction with the other being a straight spur
typical of the group; and 2) a central knob may be present.
Discoaster neohamatus is often considered synonymouswith D. calcaris (Gartner, 1967). Both species have asymmetric bifurcations, but in D. calcaris both bifurcations
are relatively straight, the shorter only deviating slightly
from ray axis. In D. neohamatus one of the bifurcations
curves and the other is a straight spur characteristic of the
Discoaster hamatus group (Figure 3). Discoaster neohamatus tends to have rays that are more delicate and thin
than those of D. calcaris.
Occurrence: The range of D. neohamatus in the
Leg 154 and GoM is Zones NN11b (7.086Ma) to NN9(10.800Ma; Table 1).
Discoaster calcaris Gartner, 1967
Pl. 4, figs 9, 12
1967 Discoaster calcaris Gartner (pro parte), p. 2, pl. 2,
figs. 1, 3a–b; non figs. 2a–b
Remarks: Discoaster calcaris has six long arms withnarrow, asymmetric bifurcations. The longer limb of thebifurcation is straight (aligned with the ray). The shorter
limb of the bifurcation is a spur that deviates slightly fromthe ray axis. In D. neohamatus, the longer limb of its
asymmetric bifurcation curves and bends proximally, as is
typical of the D. hamatus group (Figure 3). Gartner (1967)203

did not mention size in his description of D. calcaris, only
highlighting that it is a very large species. The size rangeof specimens cited above and those illustrated herein is
13.6–20.8#m.
Occurrence: The HO of D. calcaris has a general
association in the GoM with the stratigraphic horizon(Zone NN11b) marked by the HOs of D. bergenii and D.
loeblichii. In Leg 154, this horizon and the HO of D. calcaris is dated at 6.801Ma (Table 1; Blair et al., 2017; thisvolume). The LO of D. calcaris is also well-constrainedin both the GoM and Leg 154, occurring in both justbelow the HO of D. exilis (10.490Ma; Table 1), and dated
i* DZ\@D)Ii b_jdZ\Z'@& <C$<]C@K]D^ DC)\@MDC@\@O3a\
Some GoM workers include D. calcaris within D. neohamatus, but D. calcaris has an older, Late Miocene extinction (Table 1).
4.6 Discoaster loeblichii Group(Plate 4; Figure 5)
The Discoaster loeblichii Group is characterized by sixrayed forms with unequal, asymmetric bifurcations thatall bend in the same direction (Figure 5; Bukry, 1971b).
Two new morphotypes of D. loeblichii, separated by their
ray length and bifurcation thickness, are described here
as new species, D. breviloeblichii and D. pachyloeblichi.
GoM specimens in this group often possess broken rays
and are poorly preserved; therefore, three full rays must
be present to make a convincing identification. Discoasterloeblichii and its morphotypic splits provide stratigraphic
events within the Upper Miocene (Zone NN11b) in the
GoM (Figure 5).
Discoaster breviloeblichii Browning & Bergen,sp. nov.
Pl. 4, figs 18–21
Derivation of name: From the Latin brevis, meaning
short, and loeblichii, after Alfred R. Loeblich Jr.
Diagnosis: Discoaster with a large center and six shortrays that have asymmetric bifurcations
Description: Large asterolith measuring 8–10.8#m
with six short, broad rays. The rays flare slightly towards
the large center, whose diameter is about equal to thelength of the rays. The rays flare peripherally to form
unequal bifurcations that bend slightly out of the plane of
the rays. The direction of the resulting asymmetric bifurcation is always the same for all rays. The central area isornamented by six depressions around a small distal stem.
Remarks: Discoaster breviloeblichii is described fora short-rayed form of the D. loeblichii group and is thesmallest of the three species. Discoaster pachyloeblichii
has longer rays and thicker bifurcations (Figure 5). In
the BP GoM lexicon, this was referred to as D. loeblichii“stubby”.
Holotype: Pl. 4, fig. 18
Type Locality: DSDP Leg 68, Hole 502, Caribbean
Sea

204

Browning et al.

Zone

Epoch/
Stage

Messinian

6.0

CN9b

7.246

NN11a

CN9a

NN10

CN8b

9.0

8.738

7.332

8.738

7.374

D. breviloeblichii sp. nov.

8.5

NN11b

D. pachyloeblichii sp. nov.

8.0

D. loeblichiiGroup

D. loeblichii

7.5

Okada
Martini & Bukry(1971) (1980)

6.821

LATE

7.0

MIOCENE

6.5

Tortonian

Age
(Ma)
5.5

8.670

Figure 5: Range diagram of the Discoaster loeblichii Group for the late Miocene. Ranges, as well as new ages for the NN (Martini, 1971) and CN(Okada & Bukry, 1980) zonations, are derived from calibrated ages in ODP Leg 154 core samples as well as the Gulf of Mexico

Type Level: Sample 502-50-1, 19–20cm (209.89m),
Subzone NN11a, Upper Miocene
Occurrence: The HO of D. breviloeblichii is observed
just below that of D. pachyloeblichii in the BP GoM
framework, as well as Leg 154, and is dated at 7.374Ma
b/ihEL Da\ /HL J4 gi+ 0h+L,'LN i* =\$>ZIi b_jdZ\ZCC&
926C-22H-5, 73–74cm) within NN10 at Leg 154.
Discoaster loeblichii Bukry, 1971aPl. 4, fig. 17
1971 Discoaster loeblichii Bukry; p. 315–316, pl. 4,
figs. 3–5
Remarks: Bukry (1971a) described D. loeblichii as having “distinctive unequal bifurcations that are bent slightly
out of the plane of the rays” and “sense of direction of theresulting asymmetric bifurcation is always the same for all
six rays”. In the GoM, recovered specimens are often missing rays and bifurcations, so at least three full rays with
their bifurcations are needed to have any assurance of thedirection. The ray bifurcations are diagnostic and sharedwith the two related new species described herein, which
are differentiated either by ray length (D. breviloeblichii)
or bifurcation thickness (D. pachyloeblichii). Discoasterloeblichii has long rays and thin (delicate) bifurcations(Figure 5). These three morphotypes are separated as species, and BP has long recognized their tops (extinctions) as
different and stratigraphically useful in GoM wells. Bukry(1971a) gives a size range of 11–16#m for the species,
although he described it as small to medium-sized.

Occurrence: The HO of D. loeblichii is a long-standing
marker in the GoM, used by all three heritage companies. It has been associated in the GoM with the HOs of
D. bergenii and D. calcaris in deep-water wells. This
stratigraphic horizon and the HO of D. loeblichii has been
dated at 6.821Ma in Leg 154 (Table 1; Blair et al., 2017;
this volume). The LO of D. loeblichii is also wellconstrained in the GoM and Leg 154, occurring just below
the HO/INC of D. prepentaradiatus plautus (8.806Ma;
Table 1). In Leg 154, D. loeblichii and D. pachyloeblichii
have LOs at 8.738Ma (Table 1).
Discoaster pachyloeblichii Browning & Bergen,sp. nov.
Pl. 4, figs 13–16
Derivation of name: From the Greek pachys, meaning
short, and loeblichii, after Alfred R. Loeblich Jr.
Diagnosis: Discoaster having six long rays with thick,asymmetric bifurcations that bend slightly out of the planeof the rays
Description: Large to very large asterolith with
six long rays. The rays flare slightly towards the center,
whose diameter is less than the length of the rays. The
rays flare peripherally to form unequal bifurcations that
bend slightly out of the plane of the rays. The direction of
the resulting asymmetric bifurcation is always the samefor all rays. The central area is ornamented by six depressions around a small distal stem. Size = 11.6–14.0#m (twospecimens)

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

Remarks: Discoaster pachyloeblichii is distinguishedfrom D. loeblichii by having thicker bifurcations. The
two species are otherwise nearly identical. Although theirtaxonomic distinction is subtle, their stratigraphic tops
are widely disparate in the GoM (estimated 420ky). Discoaster breviloeblichii is a smaller species having a larger
center and shorter rays, but its stratigraphic range is nearly
the same as D. pachyloeblichii (Figure 5). In the BP GoM
lexicon, D. pachyloeblichii was referred to as D. loeblichii“thick”.
Holotype: Pl. 4, fig. 16
Type Locality: DSDP Leg 68, Hole 502, Caribbean Sea.
Type Level: Sample 502-48-1, 90–91cm (201.80m),
Subzone NN11a, Upper Miocene
Occurrence: The HO of D. pachyloeblichii is coeval
in the BP GoM framework and Leg 154 and dated as
7.332Ma (Zone NN11b; Table 1). The LO of D. pachyloeblichii gi+ Ni*LN G1 JLI D@' i* =\>)=Ii b_jdZ\ZC'& <C$"]
22H-4, 95–96cm).
4.7 Discoaster variabilis Group(Plate 5; Figure 6)
The Discoaster variabilis Group is characterized by large,
6-rayed species of Discoasters with broadly bifurcatedrays. Martini & Bramlette (1963) originally used D. variabilis for all asteroliths with three to six rays. Specimensshow bifurcate ray tips and a stellate central knob; however, several species within in this group can be distinguished based on the general width of the bifurcation
angle, overall size and presence of a double bifurcation(Bukry & Percival, 1971; Bukry, 1973a,b; Stradner, 1973;
this study, Figure 6). The extinctions of taxa within thisgroup are stratigraphically useful in the GoM within the
Pliocene Zones NN16 and NN15, and in the Upper Miocene Zone NN11b (Table 1; Figure 6). We discuss threedescribed species from this group: D. variabilis, D. pansus
and D. icarus. One new species is described, Discoasterpansulus.
Discoaster variabilis Martini & Bramlette, 1963
Pl. 5, figs 1–2
1963 Discoaster variabilis Martini & Bramlette (proparte), p. 854, pl. 104, figs. 4–7; non figs. 8–9
Remarks: Martini & Bramlette (1963) described D. variabilis as asteroliths with three to six long rays with a stellate central knob and bifurcations. They also note proximal
ridges along the median ray axes, but this is typical ofmany Neogene species of Discoaster. Martini & Bramlette(1963) also mentioned that some specimens may have double bifurcations; we now place these forms in D. icarus.
Both D. decorus and D. pansus were originally described as
subspecies of D. variabilis. Discoaster decorus has narrowbifurcations while D. pansus and D. pansulus have exceptionally wide bifurcations that nearly touch. Discoastervariabilis has bifurcations whose breadth is intermediate
between these two species (Figure 6).

205

Occurrence: The HO of D. variabilis has long beenutilized as a Pliocene GoM marker (mid-Zone NN16) by
BP, and this stratigraphic horizon is dated as 2.968Ma(Leg 154; Table 1) where the planktonic foraminifera
marker Globorotalia multicamerata is also used to define
this stratigraphic horizon.
Discoaster pansulus Browning & Bergen, sp. nov.
Pl. 5, figs 3–5
Derivation of name: From the Latin pansulus (diminutive), meaning spread, stretch, extend
Diagnosis: An asterolith measuring less than 15#mwith six long rays that flare to form very broad bifurcations nearly perpendicular to the rays.
Description: Medium to very large asterolith with six
long rays. The rays flare peripherally to form very broad,symmetric bifurcations that are almost perpendicular to
the rays. The center is small to medium-sized, and a small
central stem is present. In some specimens, ridges radiate down the median of the rays. Specimens measured areless than 15#m; Size = 10.0–14.0#m (five measured specimens).
Remarks: Discoaster pansulus is described for specimens less than 15#m, previously referred to as Discoastercf. pansus within BP GoM. Discoaster pansus is reserved
for specimens larger than 15#m.
Holotype: Pl. 5, fig. 4Type Locality: ODP Leg 154, Hole 926A, Ceará Rise,
western equatorial Atlantic
Type Level: Sample 926A-23-5, 1–3cm, (9.326Ma_jdZ\ZC=a k01L HHDZ^ 5..L, IG0OL1L
Occurrence: The HO D. pansulus in Zone NN15 is
Ni*LN i* '\Z)CIi b_[dZ\ZD$& <C$8]DCK]$^ 'CM')O3a G1
Leg 154.
Discoaster pansus (Bukry & Percival, 1971) Bukry,
1973bPl. 5, figs 6–7
1971 Discoaster variabilis pansus Bukry & Percival,
p. 129, pl. 3, figs. 8–9
1973 Discoaster pansus (Bukry & Percival) Bukry, p. 678,
pl. 4, fig. 25
Remarks: Bukry & Percival (1971) characterized D. pansus as a large, six-rayed species of Discoaster withbroadly bifurcated tips that are nearly perpendicular
to the rays. They remarked that D. decorus differed inhaving very narrow, small bifurcations and D. variabilis in having moderately-sized and angled bifurcations
intermediate between the other two species. Bukry& Percival (1971) gave a size range of 15–25#m forthe species; smaller specimens between 15.4–15.8#m
are illustrated herein (Plate 5). Discoaster pansulus isreserved for specimens <15#m and D. pansus for those>15#m.
Occurrence: The HRO of D. pansus is a long-utilized
BP GoM marker and dated at 4.244 in Leg 154 (Table 1).

206

Browning et al.

Zone

Epoch/
Stage

Okada
Martini & Bukry(1971) (1980)

PLE. EARLY

NN19c CN13b

MIDDLE

Zanclean

CN12b
2.968

NN16

CN12a

NN15

NN14

Messinian

4.032
4.244

CN11a
CN10c
CN10b

NN12a

CN10a

NN11b

CN9b

NN11a

CN9a

6.756
HRO6.832

7.246

Tortonian

LATE

6.5

MIOCENE

Overlapping GoM/Leg 154 range

NN10

CN8b
CN8a

D. icarus

EARLY

6.0

8.5

CN12c

NN13

5.5

8.0

NN17

NN12b

5.333

7.5

CN12d

CN11b

5.0

7.0

NN18

D. variabilis Group

3.600

4.0
4.5

NN19a CN13a

D. pansus

3.5

PLIOCENE

3.0

2.58

NN19b

D. pansulus sp. nov.

2.5

Piacenzian

LATE

2.0

Gelasian

1.80

D. variabilis

Age
(Ma)
1.5

LO21.222

LO14.280

8.785

Figure 6: Range diagram of the Discoaster variabilis Group. Ranges, as well as new ages for the NN (Martini, 1971) and CN (Okada & Bukry, 1980)
zonations, are derived from calibrated ages in ODP Leg 154 core samples as well as the Gulf of Mexico

Discoaster icarus (Stradner, 1973)
Pl. 5, figs 8–9
1963 Discoaster variabilis Martini & Bramlette (proparte), p. 854, pl. 104, fig. 8; non figs. 4–7, 9
1973 Discoaster icarus Stradner, p. 1138, pl. 41, figs. 7,
10–11; pl. 42, figs. 1–6, 9, 10

Remarks: Stradner (1973) diagnosed D. icarus as “a species of Discoaster of the D. variabilis group with rays terminating in a wide-angle of bifurcation of branches with‘flaps’ between the branches” (Figure 6). These “flaps” are
the “double bifurcations in some specimens” mentioned
in the description of D. variabilis by Martini & BramletteLate Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

(1963). Stradner (1973) mentioned a size of 30#m andsmaller but illustrated nine specimens by light photomicrograph with a size range between 10.7–24.1#m. Discoaster icarus was not subdivided into size categories in
our Leg 154 research.
Occurrence: The HRO of D. icarus has long-beenutilized as an Upper Miocene GoM marker by BP andreferred to as D. cf. icarus (small) and has been dated in
Leg 154 at 6.832Ma (Table 1). The HO of D. icarus was
0h+L,'LN i* $\>@$Ii G1 JLI D@' b_[dZ\ZC)& <C$8]D=]$^
91–92cm).
4.8 Minylitha convallis Group (Plate 5)
The Minylitha Group is characterized by birefringent T- andI-shaped bars in side view position that appear as kite-shaped
wedges in the basal position (Bukry, 1972; Theodoridis,
1984). The HO and HRO of M. convallis are important
GoM heritage markers in Upper Miocene Zone NN11a. This
group includes one well-established species, M. convallis,
and a new species described here, M. cancellata.
Minylitha convallis Bukry, 1973b emend.
Theodoridis, 1984
Pl. 5, figs 11–13
1973b Minylitha convallis Bukry, p. 679, pl. 3, figs. 12–18
1984 Minylitha convallis Bukry, Theodoridis, p. 84, pl. 4,
figs. 1–7
Remarks: Minylitha convallis has T-shaped or I-shaped
cross sections that display a bright, 1st order white birefringence; in the distal position the kite-shaped wedges aremostly dark in cross-polarized light except for their faintly
birefringent outline.
Occurrence: The HO of M. convallis is coeval in the
GoM and Leg 154, where it has been dated at 7.265Ma(Table 1). The HRO of M. convallis, paired with the HO of
Helicosphaera orientalis in the GoM framework, is associated with its first downhole increase of M. convallis in
the Leg 154 section and dated at 7.848Ma in Zone NN11a(Table 1; Boesiger et al., 2017; this volume). The LO of
M. convallis is dated at <\>'<Ii b_jdZ\ZDD& <C$<]C']C^
61–63cm).
Minylitha cancellata Browning & Bergen, sp. nov.
Pl. 5, figs 14–22
Derivation of name: From the Latin cancellatus, meaning latticed, cross-barred, grilled
Diagnosis: Minylitha with a thickened longitudinalridge(s) and multiple, parallel, transverse ridges
Description: A small triangular to sub-pentagonalnannolith. A prominent longitudinal ridge or paired ridges
run the length of the nannolith and are more birefringent(1st order white) than the rest of the nannolith. Three to fiveparallel transverse ridges radiate from either side of thelongitudinal ridge(s) giving the impression of a canceollate pattern. Forms observed have a Y-shaped cross-section
with the longitudinal ridge forming the base of the “Y”

207(Pl. 5, figs 17–18). Length to width ratios are roughly
0.85–1.17 (10 specimens). Size = 3.2–5.6#m
Remarks: Minylitha convallis has either a T-shaped
or I-shaped cross section, as opposed to the Y-shaped
cross-section of M. cancellata. Both species are made oftriangular wedges, but M. cancellata is distinguished byits series of transverse ridges. In overgrown specimens,
the transverse ridge may appear as one solid ridge.
Holotype: Pl. 5, figs 15–16
Type Locality: Bolli Collection, Trinidad
Type Level: KR23425, Globorotalia menardi Zone,
NN9, Upper Miocene
Occurrence: Minylitha cancellata is restricted to theUpper Miocene (NN9–NN10); the stratigraphic range
is coeval in the GoM and Leg 154. Its range is dated
K,03 DZ\DCC b_jdZ\ZC)& <C$<]C']@^ D'$\@MD'=\@O3a *0
9.326Ma (Table 1) in Leg 154.
Acknowledgements
We are grateful to BP GoM Exploration for their supportand encouragement in the publication of this research aswell as Graham Vinson, Liz Jolley, Tim Hill and John Farrelly. We are appreciative of the BP GoM teams in Exploration and Production. These groups were fundamental in the
integration and application of these biostratigraphic events
to broaden the understanding of the geologic description
within the subsurface of the GoM. This paper was greatly
improved by suggestions from the reviewers Jim Pospichal
and Jeremy Young. The authors would like to also thank BP
for its financial support of the ODP Leg 154 sampling andresearch as well those involved in the acquisition, preparation and analyses of materials involved in this study. We’realso grateful to the Integrated Ocean Drilling Program forthe use of ODP Leg 154 materials. Of course, we’d like tothank the authors’ families for their patience and support asthese five papers were concurrently written and reviewed.
Special thanks are extended to Jim Newell, whose workfor two of the BP heritage companies contributed greatly
to this work. We also thank Jim Pospichal, Richard White,
Scott Staerker and the late Ralph Salomon for discussions.
Thanks to Woody Wise and Katrina Perch-Nielsen forteaching us the basics and to David Watkins for passing
this onto the new generation.
Finally, it has not been lost on the authors that these
five papers introduce a beastly barrage of brand-new bugs,
their authors beginning with B. Not since Wind & Wise
in Wise & Wind (1977) has this had the potential for confusion. From Blair, Bergen, Browning and Boesiger… weapologize, briefly.
References

Bergen, J.A., de Kaenel, E., Blair, S., Boesiger, T. & Browning,
E. 2017. Oligocene-Pliocene taxonomy and stratigraphy of
the genus Sphenolithus in the circum North Atlantic Basin:
Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton
Research, 37(2/3), 77–112.

208

Browning et al.

Bergen, J.A., Truax III, S., de Kaenel, E., Blair, S., Browning, E.,
Lundquist, J., Boesiger, T., Bolivar, M. & Clark, K. 2017 (inprep). BP Gulf of Mexico Neogene Astronomically-Tuned
Time Scale.
Blair, S., Bergen, J., de Kaenel, E., Browning, E. & Boesiger,
T. 2017. Upper Miocene-Lower Pliocene taxonomy and stratigraphy in the circum North Atlantic Basin: radiation andextinction of Amauroliths, Ceratoliths and the D. quinqueramus lineage. Journal of Nannoplankton Research, 37(2/3):
113–144.
Boesiger, T., de Kaenel, E., Bergen, J., Blair, S. & Browning,
E. 2017. Oligocene to Pleistocene taxonomy and stratigraphy of the genus Helicosphaera and other placolith taxa inthe circum North Atlantic Basin. Journal of Nannoplankton
Research, 37(2/3): 145–175.
Bolli, H.M. 1957. Planktonic foraminifera from the OligoceneMiocene Cipero and Lengua formations of Trinidad,
B.W.I. In: A.R. Loeblich, H. Tappan, J.P. Beckmann,
H.M. Bolli, E.M. Gallitelli & J.C. Troelsen (Eds). Studies
in Foraminifery. Bulletin of the U.S. National Museum,
215: 97–123.
Bramlette, M.N. & Riedel, W.R. 1954. Stratigraphic value of
Discoasters and some other microfossils related to Recent
coccolithophores. Journal of Paleontology, 28(4): 385–403.
Bukry, D. 1971a. Cenozoic calcareous nannofossils fromthe Pacific Ocean. San Diego Society of Natural History
Transactions, 16(14): 303–327.
Bukry, D. 1971b. Discoaster evolutionary trends. California
University Scripps Institute of Oceanography Contributions,41: 465–474.
Bukry, D. 1972. Further comments on coccolith stratigraphy,
Leg 12, Deep Sea Drilling Project. In: A.S. Laughton, W.A.
Berggren et al. (Eds). Initial Reports of the DSDP, 12:1071–
1084.
Bukry, D. 1973a. Low-latitude coccolith biostratigraphic zonation. In: N.T. Edgar, J.B. Saunders et al. (Eds). Initial Reportsof the DSDP [U.S. Government Printing Office, Washington],
15: 685–703.
Bukry, D., 1973b. Coccolith stratigraphy, eastern equatorial
Pacific, Leg 16, Deep Sea Drilling Project. In: W.B.F. Ryan,
K.J. Hsü et al. (Eds). Initial Reports of the DSDP [U.S.
Government Printing Office, Washington], 16: 653–711.
Bukry, 1973c. Phytoplankton Stratigraphy, Deep Sea Drilling
Project Leg 20, Western Pacific Ocean. In: B.C. Heezen, I.D.
Macgregor et al. (Eds). Initial Reports of the DSDP [U.S.
Government Printing Office, Washington], 20: 307–317.
Bukry, D. & Bramlette, M.N. 1969. Some new and stratigraphically useful calcareous nannofossils of the Cenozoic. Tulane
Studies in Geology and Paleontology, 7(3): 131–142.
Bukry, D. & Percival, S.F. 1971. New Tertiary calcareous nannofossils. Tulane Studies in Geology and Paleontology, 8(3):123–146.
Ellis, C.H., Lohman, W.H. & Wray, J.L. 1972. Upper Cenozoic
Calcareous Nannofossils from the Gulf of Mexico (Deep Sea
Drilling Project, Leg 1, Site 3). Colorado School of Mines:
1–103.

De Kaenel, E., Bergen, J., Blair, S., Boesiger, B. & Browning, E.
2017. Latest Oligocene to Middle Miocene Discoaster andCatinaster lineages. Journal of Nannoplankton Research,
37(2/3): 215–244.
Denne, R.A. 2008. Utilizing abundance changes of new andnon-standard calcareous nannofossil taxa to increase biostratigraphic resolution in expanded continental margin deposits:
examples from the Middle and Lower Miocene of the Gulf
of Mexico. Gulf Coast Association of Geological Societies
Transactions, 58: 227–239.
Gartner, S. Jr. 1967. Calcareous nannofossils from Neogene of
Trinidad, Jamaica, and Gulf of Mexico. The University of
Kansas Paleontological Contributions, 29: 1–7.
Gartner, S. Jr. 1969. Correlation of Neogene planktonic andcalcareous nannofossil zones. Gulf Coast Association of
Geological Societies Transactions, 19: 585–599.
Gradstein, F.M., Ogg, J.G., Schmitz, M. & Ogg, G. 2012. The
Geologic Time Scale 2012. Elsevier: 1176pp.
Hay, W.W., Mohler, H.P., Roth, P.H., Schmidt, R.R. & Boudreaux,J.E. 1967. Calcareous nannoplankton zonation of the Cenozoicof the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation. In: Symposium on the geological history of
the Gulf of Mexico, Antillean Caribbean region. Gulf Coast
Association Geologic Societies Transactions, 17: 428–480.
Hojjatzadeh M. 1978. Discoasters of the Blue Clay (middle
Miocene) of Malta and Gozo. Geological Magazine, 115(1):1–19.
Kamptner, E. 1967. Kalkflagellaten-Skelettreste aus Tiefseeschlammdes Suedatlantischen Ozeans. Annalen de Naturhistorisches
Museum Wien, 71: 117–193.
Lourens, L.J., Antonarakou, A., Hilgen, F.J., Van Hoof,
A.A.M., Vergnaud-Grazzini, C. & Zachariasse, W.J. 1996.
Evaluation of the Plio-Pleistocene astronomical timescale.
Paleoceanography, 11(4): 391–413.
Lourens, L.J., Hilgen, F.J., Shackleton, N.J., Laskar, J., Wilson, D.
2004. The Neogene Period. In: F.M. Gradstein, J.G. Ogg &A.G. Smith (Eds). A Geological Time Scale 2004. Cambridge
University Press, Cambridge: 409–440.
Martini, E. 1971. Standard Tertiary and Quaternary calcareous
nannoplankton zonation. In: A. Farinacci (Ed.). Proceedingsof the Second Planktonic Conference Roma 1970. Edizioni
Tecnoscienza, Rome, 2: 739–785.
Martini, E. & Bramlette, M.N. 1963. Calcareous nannoplankton from the experimental Mohole drilling. Journal of
Paleontology, 37(4): 845–856.
Martini, E. & Worsley, T.R. 1971. Calcareous nannofossils fromthe western equatorial Pacific Leg I. Initial Reports of theDSDP, Part 2, 7: 1471–1507.
Okada, H. & Bukry, D. 1980. Supplementary modification andintroduction of code numbers to the low-latitude coccolith biostratigraphic zonation (Bukry, 1973; 1975). Marine
Micropaleontology, 5: 321–325.
Raffi, I., Agnini, C., Backman, J., Catanzariti, R. & Pälike, H.
2016. A Cenozoic calcareous nannofossil biozonation from
low and middle latitudes:A synthesis. Journal Nannoplankton
Research, 36(2): 121–132.

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

Stradner, H. 1973. Catalogue of calcareous nannoplankton fromsediments of the Neogene in the eastern North Atlantic andMediterranean Sea. In: W.B.F. Ryan, K.J. Hsü, et al. Initial
Reports of the DSDP, 13(2): 1139–1199.
Tan, S.H. 1927. Disocasteridae incertae sedis. Proceedingsof the Section of Sciences, Koninklijke Akademie van
Wetenschappen., Amsterdam, 30: 411–419.
Theodoridis, S. 1984. Calcareous nannofossil biozonation of
the Miocene and revision of the helicoliths and discoasters.
Utrecht Micropaleontological Bulletins, 32: 1–271.

209

Wei, W. 2003. Upper Miocene nannofossil biostratigraphy
and taxonomy of Exxon Core CH30-43-2 from the Gulf
of Mexico. Journal of Nannoplankton Research, 25(1):17–23.
Young, J.R., Bergen, J.A., Bown, P.R., Burnett, J.A., Fiorentino,A., Jordan, R.W., Kleijne, A., van Niel, B.E., et al. 1997.
Guidelines for coccolith and calcareous nannofossil terminology. Palaeontology, 40: 875–912.

210

Browning et al.

Plate 1
NN18

2!m

1

D. triradiatus

926C-6H-6,19-20

NN16

2

D. tamalis

926C-9H-3,3-4

NN16

NN16

3

D. tamalis502-21-1, 112-113

NN18

NN16

4

926C-9H-2,73-75

D. tamalis (asy)5926B-7H-2,35-36

D. blackstockae

NN16

NN16

NN11a

6

926A-9H-2,89-90

D. asymmetricus
HOLOTYPE

9

13

D. trifolius

926C-7H-6,36-37

10

926B-7H-2,119-120

D. dennei

926A-24-3,108-110

926C-8H-6,21-22

NN18

11

926A-23-2,72.5-74.5

D. styzenii (asy)15

D. styzenii

20

GoM

D. extensus

23926B-22-5,116-118

D. prep. prepentaradiatus

16

D. styzenii

24

GoM

17

NN10

926A-23-2,72.5-74.5

D. prepentaradiatus plautus
NN10

NN9

GoM

21

926A-24-1,10-12

22

D. extensus

25

KR 23425

26

KR 23425

926B-22-5,15-16

NN16

NN9

NN10

D. prep. prepentaradiatus

GoM

NN9 D. extensus

D. prepentaradiatus plautus D. prepentaradiatus plautus
NN10926A-24-1,10-12

DSDP-502-50-1,19-20

NN10 HOLOTYPE

NN11a

NN10

19

12

D. neorectus

NN9

NN10

14

926B-7H-2,35-36

D. dennei

NN10926A-23-4,54.5-56.5

8

D. brouweri

NN18

NN18

NN9

18

502-21-2, 112-113

D. asymmetricus

D. dennei
HOLOTYPE

727

926A-11H-3,134-135

D. prep. prepentaradiatus D. prep. prepentaradiatus D. pentaradiatus

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

211

Plate 2
NN13

2!m

NN16

3

926C-10H-6,39-40

D. surculus (3ray)

1

NN16

NN16

4 926A-10H-3,64-66 5

D. surculus (4ray)

926B-15H-5, 2-3

926C-9H-6,15-16

D. surculus (5ray)

NN16

6

926C-10H-3,137-138

D. surculus

NN11a

NN11a

NN13

2

D. pentaradiatus
NN11b

8

502-50-1, 19-20

D. surculus

9502-50-1, 19-20

NN 1b

NN11b

D. pseudovariabilis
1

NN16

7

926B-19H-2,61-62

D. subsurculus

NN11b

1

10

13

11

1

NN 1b

NN14

NN14

12

14

502-36-1, 50-51

D. pseudovariabilis
NN16

15

NN11b
926C-10H-6,39-40

16

926C-8H-4,129-130

502-41-1, 30-31

D. pseudovariabilis

D. toralus

15502-30-1, 33-34

16

17

926A-9H-4,75-77

D. pliostellulus

NN16 HOLOTYPE

18

926C-9H-1,144-145

D. pliostellulus

19

NN16

926A-10H-2,144-145

D. pliostellulus

212

Browning et al.

Plate 3NN9

2!mHOLOTYPE

1

KR23425NN92

926A-24-3,108-110

D. tribollii

HOLOTYPE

3

NN9KR23425

NN94HOLOTYPE

NN95

D. quadribollii
NN9

NN9

6

KR23425

D. pentabollii

7KR23425

D. pentabollii
NN911

KR23425NN98KR23425

D. pentabollii
NN9

12

NN9

13

9

KR23425

HOLOTYPE

14

NN9

17

D. cauliflorus

KR23425

NN6

NN9

22

21

GoM

GoM

926A-27-2,105-107

D. exilis

D. cauliflorus

NN7

18

KR23425

D. cauliflorus

GoM

D. cauliflorus

23

NN8

Bo355

NN9

15

KR23425

20

926A-24-3,108-110

D. cauliflorus

24

NN7

25

Bo355

D. exilis

NN7

NN9

HOLOTYPE

NN7

NN7

D. exilis

KR23425

D. bollii (short arm)
NN10

19

10

NN9

KR23425NN9NN9D. bollii (long arm)

D. bollii (short arm)
NN9

D. bollii (short arm)

NN9D. pentabollii

D. bollii (long arm)

16

HOLOTYPE

NN7
N

NN7

GoM, Mississippi Canyon

26926B-25-5,133-135

D.926B-25-5,133-135
exilis (4ray)

27
D. gozoensis

Bo355

28
D. gozoensis

Bo355

29

926A-26-2,141.5-143.5

D. gozoensis

30

926A-26-2,141.5-143.5

D. gozoensis

Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster…

213

Plate 4
NN9 HOLOTYPE

2!mHOLOTYPE

1

NN9

2

926A-24-3,20.5-22.5

3

D. triuncinus

KR23425

D. bolivariae

KR23425

D. triuncinus
NN9

NN9

HOLOTYPE

6

NN9

7

926A-25-1,35-37

D. hamatus (<15)

NN9

5

4

D. bolivariae

8926A-24-3,20.5-22.5

KR23425NN99D. calcaris

NN11a

KR23425

D. hamatus (>15)
NN11a

NN11a

KR23425

NN9

12

10

926A-24-2,91-93

D. hamatus (<15)

NN9D. hamatus (<15)

502-50-1, 19-20

NN9

NN9

D. calcaris

GoM

HOLOTYPE

NN11a

NN11a

11

D. neohamatus

13

926B-20-2,37-38

D. pachyloeblichii

NN11a

NN11b HOLOTYPE

17

GoM
926A-20H-3, 50-51

D. loeblichii

18

D. pachyloeblichii

D. pachyloeblichii

16502-48-1, 90-91

NN11a

NN11a

NN11a

15

14

502-50-1, 19-20

D. breviloeblichii

19926B-20-6,133-134

D. breviloeblichii

502-48-1, 90-91

20

D. breviloeblichii

GoM

21

214

Browning et al.

Plate 5
2!m

1

NN2

926B-41-3,10-11

NN16

2

926A-10H-3,64-66

D. variabilis
NN16

D. variabilis

NN63

10.05 !m926A-27-1,131-133

D. pansulus
NN9

4

NN10

NN9
NN10

HOLOTYPE

11.05!
926A-23-5,1-3

D. pansulus

512.40!mm
926B-22-5,116-118

D. pansulus
NN11a

NN16

11
6

15.80 !m926A-11H-3,54-55

D. pansus

715.40!m
926C-11H-2,90-92

D. pansus

NN13

NN11a

8

22.50!
502A-50-1, 19-20

D. icarus
NN10

9

D. icarus

NN10

16.10!m502-50-1, 19-20

10502-30-1, 33-34

D. decorus

Minylitha convallis
NN10

NN9

HOLOTYPE

11

Minylitha convallis
NN9

GoM

12

NN9

NN9
m

13

GoM

NN9

14

Minylitha cancellata

GoM

15

17
NN9

HOLOTYPE

16

KR23425

Minylitha cancellata

19
NN9

18

Minylitha cancellata

GoM

21
NN9

20

Minylitha cancellata

GoM

NN9

22

926A-24-6,66.5-68.5

Minylitha cancellata